661644937 has 2 divisors, whose sum is σ = 661644938. Its totient is φ = 661644936.

The previous prime is 661644877. The next prime is 661644941. The reversal of 661644937 is 739446166.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 468462736 + 193182201 = 21644^2 + 13899^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661644937 is a prime.

It is not a weakly prime, because it can be changed into another prime (661644967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330822468 + 330822469.

It is an arithmetic number, because the mean of its divisors is an integer number (330822469).

Almost surely, 2^661644937 is an apocalyptic number.

It is an amenable number.

661644937 is a deficient number, since it is larger than the sum of its proper divisors (1).

661644937 is an equidigital number, since it uses as much as digits as its factorization.

661644937 is an evil number, because the sum of its binary digits is even.

The product of its digits is 653184, while the sum is 46.

The square root of 661644937 is about 25722.4597774008. The cubic root of 661644937 is about 871.3814916670.

The spelling of 661644937 in words is "six hundred sixty-one million, six hundred forty-four thousand, nine hundred thirty-seven".